Bloomberg adviser Kevin Sheekey told The Washington Post, which first reported the donation to the Senate Majority PAC, that Bloomberg was disappointed in Republican Senate leadership and believed Democrats would be mobilized to vote in the upcoming midterms by the uproar over sexual assault allegations against Supreme Court nominee Brett Kavanaugh.

The $20 million donation, which Bloomberg advisers Marc La Vorgna and Howard Wolfson confirmed to POLITICO, will help Democrats in a difficult battle to reclaim the Senate. Republicans hold a narrow 51-49 majority in the chamber. But Democratic senators are up for reelection in 10 states that President Donald Trump won in 2016 — putting the party on defense in much of the country and rendering it difficult for Democrats to retake the chamber, even in a favorable political climate.